The "glass run" in an automobile door is the rubber seal mounted in the sliding window channel in the window frame. There is usually a "belt seal" along the lowermost edge of the window frame through which the window is extended and retracted from the interior of the door.
The sliding/wiping seal fit between the glass run and belt seals and the edges of the window creates frictional wear on the seals, which are expected to withstand tens or hundreds of thousands of cycles while maintaining an effective seal with the window. The reliability of the seals and their resistance to wear is therefore critical to the long-term operation of the entire window assembly. In an automobile the window assembly is a fairly integral part of the door, and repair or replacement of the seals can be difficult and expensive.
The current method of testing the effectiveness and wear life of the glass run and belt seals is to put the seals in an actual production-line door and to test them over hundreds or thousands of cycles at the automobile manufacturer's facility. There are a number of problems with this method. First, if the seal is defective, the entire door and window frame must be disassembled, and the seal must be replaced, returned and diagnosed by the seal manufacturer. Second, this testing method cannot anticipate the minimum and maximum tolerance variations from door to door. Third, the window actuator motors are prone to failure, and because they overheat easily they are operated for seal testing at about one cycle per minute. This is very slow when a seal's failure limit of tens of thousands of cycles is being tested.
Another difficulty in testing glass run seals is the frequent need to test them under specific environmental conditions, for example hot conditions simulating desert use and cold conditions simulating winter use. Current methods of testing make it difficult and expensive to test under these conditions.